Initial values for the fit parameters		Plot description
Slope:		X-axis:
Axis intercept:		Y-axis:
Your data file:		Plot title:

The argument parameters can be omitted. In this case the defaults:

    Slope = -1.0 ,  Intercept = 11.0

are used. The data file should contain a table with the measured data. It must contain four columns:

    X-Value   Error_of_X   Y-Value   Error_of_Y

Here is an example file: partb_testdata.txt .

The numeric results will be both shown on this Webpage and plotted in a postscript file.
You can save that file, print and attach it to your report.

Unfortunately, GNUPlot cannot make fits of data with two quantities measured with errors. The calculation is performed using the Linux program twoerrors.exec which you can download.
Start it as follows:

    twoerrors.exec A B < datafile

A is the start value for the slope of the straight line (the same as above),
B is the start value for the intercept of the straight line.
Only float numbers can be specified for arguments, e.g.: 5.2 or -3.0 or 1.e-3.

The program is based on the package Minuit from the CERN program library.
Here is the source code in fortran: twoerrors.f .